1. Field of the Invention
The present invention relates to a battery module including a container with a battery therein, which container when replaceably mounted on a compact electric appliance such as, for example, a mobile phone, forms a part of an outer surface of the compact electric appliance.
2. Description of Background Art
In recent years, a relatively fierce competition is taking place among manufacturers to downsize battery-driven compact electric appliances including, for example, mobile phones as small as possible and, encased battery units used in those electric appliances as one of major components are not an exception. To cope with this trend, attempts have been made to downsize the encased battery unit by flattening the outer configuration of a battery and to render it to be lightweight by employing aluminum, in place of iron, as a material for a battery casing. Also, further reduction in size and weight is obviously possible that if the wall thickness of the battery casing for accommodating such a battery is reduced as small as possible to an extent necessitated and, at the same time, outer surfaces of a battery are held in tight contact with inner surfaces of the battery casing.
However, to sustain the battery power required in the compact electric appliance, the battery must have an adequate capacity. The mobile phone, for example, makes use of a generally rectangular flattened battery and any attempt to reduce the thickness of this type of battery requires increase of the area of front and rear surface areas of the battery, which necessarily leads to reduction in strength of a central region of each of the front and rear surface areas of the battery. It has been well known that although if a casing for the battery is made of iron, the battery can retain its shape by the effect of rigidity of the iron material, the use of aluminum as a material for the casing will result in insufficient rigidity for a given thickness, resulting in the possibility that the front and rear surface areas of the battery will be distended during the cycle of charging and discharging.
In most mobile phones, a battery providing a power source is employed in the form of a battery module including a container accommodating therein at least one battery or cell. In such case, to eliminate the above discussed problems, the rigidity may be increased by the use of the container having an increased wall thickness and/or a space, may be provided between the inner surface of the container and the surface of the battery or cell to accommodate expansion of the front and rear surface areas of the battery, thereby minimizing deformation of the battery module as a whole and also avoiding any possible adverse influence that may be brought on the compact electric appliance with which the battery module is used. However, these attempts are obviously contrary to the attempt to reduce the size and weight.
In an attempt to eliminate the numerous problems discussed above, the inventors of the present invention have conducted a series of studies on the interface between the compact electric appliance and the battery module. Deformation should be minimized in order for the interface between the compact electric appliance and the battery module to exhibit a sufficient strength with which they are engaged with each other. On the other hand, the inventors have found that since a casing for most of the compact electric appliances is formed to have a chamfered or rounded outer appearance, a slight swelling of the casing resulting from deformation of the battery or cell will not be noticeable. Speaking differently, the real problem does not lie in deformation of the battery module as a whole, and no adverse influence resulting from deformation of the battery or cell will be brought about only if means is provided to prevent any possible deformation from occurring at the interface with the compact electric appliance.
The present invention is therefore based on the foregoing finding and is intended to provide a battery module effective to prevent an undesirable mechanical bearing, brought about by deformation of the battery module, from being imposed on the compact electric appliance, while the size and the weight of the battery module as a whole are reduced as small as possible, for which while deformation of the container in the battery module in such a direction as to result in contact with the compact electric appliance is suppressed, the deformation of the battery or cell is guided outwardly of the compact electric appliance.
The battery module according to the present invention is of a design which when replaceably mounted on the compact electric appliance such as, for example, a mobile phone, forms a part of the outer surface of such compact electric appliance. This battery module includes a battery having a flattened outer configuration and tolerated to deform in a direction conforming to the direction of thickness thereof, and a container tightly enclosing the battery.
Also, deformation of the container in such a direction as to result in contact with the compact electric appliance when mounted on the compact electric appliance is suppressed, but deformation of the container in a direction opposite thereto and outwardly of the compact electric appliance is tolerated.
The battery module may be so constructed that deformation thereof in one of opposite directions across the thickness of the battery, that is, in a direction towards a casing of the compact electric appliance can be suppressed. In such case, suppression of the deformation of the battery can be achieved by selecting the rigidity of surfaces of the container that are tolerated to deform, to a value lower than that of surfaces thereof that are prohibited from deforming, or by forming a recess at a center region of the surfaces of the container that is suppressed from being deformed.
The container may be of a design capable of retaining peripheral edges of the battery and may have a gap between the battery and a contact surface thereof across the thickness of the battery for accommodating deformation of the battery, which gap may be defined. In such case, the space to be formed within the container may be formed by defining a recess in the center region of the surface thereof facing the battery, or by the thickness of a retaining member for connecting a periphery of the battery to the inner surface of the container.
Thus, according to the present invention, while the deformation of the container in the battery module in such a direction as to result in contact with the compact electric appliance is suppressed, deformation of the battery in a direction outwardly of the compact electric appliance is tolerated. Accordingly, it is possible to increase the reliability of the battery firmly retained in the battery module while. the size and the weight of the battery module as a whole can be reduced as small as possible and the capability of engagement with the compact electric appliance resulting from deformation of the battery module is maintained.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.